HR: 1340h
AN: PP33A-1010    [Abstracts]
TI: A New Look at the Early Eocene Arctic Climate in CCSM3: Sensitivity to pCO2 and Basin Geography
AU: * Shellito, C
EM: lucinda.shellito@unco.edu
AF: University of Northern Colorado, Earth Sciences Program Campus Box 100, Greeley, CO 80639, United States
AU: Kiehl, J
EM: jtkon@ucar.edu
AF: National Center for Atmospheric Research, 1850 Table Mesa Dr., Boulder, CO 80305, United States
AU: Lamarque, J
EM: lamar@ucar.edu
AF: National Center for Atmospheric Research, 1850 Table Mesa Dr., Boulder, CO 80305, United States
AU: Sloan, L
EM: lcsloan@pmc.ucsc.edu
AF: University of California, Santa Cruz, 1156 High St., Santa Cruz, CA 95064, United States
AB: We present results from new Eocene climate modeling experiments that support the role of high pCO₂ in maintaining Arctic warmth during the early Cenozoic. The fully-coupled NCAR Community Climate System Model (CCSM) (v.3) was employed with early Eocene geography in two experiments to test the sensitivity of climate to a large increase in pCO₂ (from 2x to 8x pre-industrial pCO₂). In a third experiment, we open an ocean passageway from the Eocene Arctic to the Pacific to establish the maximum sensitivity of Arctic climate to neighboring oceans, as periodic connections with adjacent ocean basins may have influenced Arctic climate at this time. To compare with the 8xCO₂ scenario, we also run this open Arctic experiment at 8xCO₂. In the CO₂ sensitivity experiments, annual average global mean temperature rose ~3.4C with a quadrupling of pCO₂, consistent with previous modeling studies. The greatest warming occurred in the Arctic Polar region, and is due in part to reduced sea ice formation in the high pCO2 experiment. Arctic surface temperatures from the high pCO₂ scenario (8xCO₂) agree most closely with new proxy data from the early and middle Eocene Arctic. Mean annual temperature estimates from various proxies range from ~10- 15C. Modeled Arctic temperatures range from 2-8C, and begin to approach 10C along the North American coast. While still somewhat lower than that estimated from proxies, it is important to note that in this 8xCO₂ experiment, wintertime Arctic air temperatures remain mostly above freezing. Opening the Arctic to the influence of the Pacific in the third experiment has the effect of warming the average sea surface temperature in the Arctic basin by ~4C. Central Arctic ocean temperatures warm by as much as 5C to 7C. Temperatures are as high as 10C along northern Europe in the open Arctic scenario.
DE: 1622 Earth system modeling (1225)
DE: 1626 Global climate models (3337, 4928)
DE: 9606 Paleogene
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting